1. Field of the Invention
The present invention relates to a thin-film device incorporating a conductor layer and a terminal electrode connected to the conductor layer.
2. Description of the Related Art
With increasing demands for reductions in dimensions and thickness of high frequency electronic apparatuses such as cellular phones, reductions in dimensions and profile of electronic components mounted on the high frequency electronic apparatuses have been sought. Some of the electronic components have such a configuration that insulating layers and conductor layers are formed on a substrate through the use of thin-film forming techniques. Such electronic components formed through the use of thin-film forming techniques are called thin-film device in the present patent application.
In a thin-film device, terminal electrodes are provided for connecting conductor layers to an external circuit. Here, a portion of the thin-film device other than the terminal electrodes is called a device main body. Each conductor layer connected to the terminal electrodes includes a wiring portion, for example, and is formed so that an end face of the wiring portion is exposed at a side surface of the device main body. In this case, the terminal electrodes are disposed on the side surfaces of the device main body, for example, so as to be connected to the end faces of the wiring portion.
Here is given an example of a method of manufacturing a thin-film device wherein the terminal electrodes are disposed on the side surfaces of the device main body. In the method, first, a thin-film device substructure is fabricated by forming layers such as conductor layers corresponding to a plurality of thin-film devices on a single wafer (a substrate). The substructure includes a plurality of preliminary device main body portions each of which will be a device main body. Furthermore, in the substructure, there are provided portions to be removed between respective adjacent ones of the preliminary device main body portions. Next, the plurality of preliminary device main body portions are separated into a plurality of device main bodies by cutting the substructure at positions of the portions to be removed. By cutting the substructure in such a manner, side surfaces of the device main bodies are formed, and end faces of wiring portions to be connected to terminal electrodes are exposed at the side surfaces. Next, the terminal electrodes are formed on the side surfaces of the device main bodies.
To reduce the dimensions and profile of a thin-film device, it is effective to reduce the thickness of layers such as conductor layers. However, according to the above-described method, a reduction in thickness of conductor layers causes a reduction in areas of the end faces of the wiring portion connected to the terminal electrodes. As a result, the regions in which the conductor layers touch the terminal electrodes are reduced in area, and accordingly it becomes difficult to secure the reliability of connection between the conductor layers and the terminal electrodes.
To avoid this problem, such a technique is conceivable that the wiring portion may be increased in width to thereby increase the area of the end faces of the wiring portion. However, this may cause a problem in the thin-film device that the density of the wiring portion is reduced and therefore it becomes difficult to reduce the dimensions of the thin-film device, or that the impedance of the wiring portion deviates from a desired value and the characteristics of the thin-film device are thereby degraded. Another problem is that there occurs an increase in area of the region of the thin-film device in which the wiring portion is located, and it is therefore difficult to reduce the dimensions of the thin-film device and the area occupied by the thin-film device.
JP 10-163002A discloses a technique wherein, in a chip-shaped electronic component in which an inner conductor film is disposed on a substrate and external terminal electrodes are connected to end faces of the inner conductor film, the end faces of the inner conductor film are tilted with respect to a sectional surface of the substrate.
JP 11-003833A discloses a technique wherein, in an electronic component in which electrodes are disposed on a substrate and external terminals are connected to end faces of the electrodes, the end faces of the electrodes on the substrate are tilted with respect to sectional end faces of the substrate.
JP 2-121313A discloses a thin-film capacitor wherein three or more inner electrode layers and two or more dielectric layers are alternately stacked on a substrate, and outer electrodes connected to the inner electrode layers are disposed on side surfaces of the substrate. JP 2-121313A discloses a technique wherein two of the inner electrode layers forming one of electrodes of a single capacitor in a circuit are laid over each other in a neighborhood of one of the side surfaces of the substrate, and one of the outer electrodes is connected to the portions of the two inner electrode layers laid over each other.
JP 5-129149A discloses a thin-film capacitor wherein four inner electrodes and four dielectric thin films are alternately stacked on a substrate, and outer electrodes connected to the inner electrodes are disposed on side surfaces of the substrate. JP 5-129149A discloses a technique wherein two of the inner electrodes forming one of electrodes of a single capacitor in a circuit are laid over each other in a neighborhood of the side surfaces of the substrate, and the outer electrodes are connected to the portions of the two inner electrodes laid over each other.
In the following description the external terminal electrodes of JP 10-163002A, the external terminals of JP 11-003833A, and the external electrodes of JP 2-121313A and JP 5-129149A are all called terminal electrodes.
As previously described, in a thin-film device in which terminal electrodes are disposed on the side surfaces of the device main body, a reduction in thickness of conductor layers causes a reduction in areas of the end faces of the wiring portion connected to the terminal electrodes, and as a result, the regions in which the conductor layers touch the terminal electrodes are reduced in area and accordingly it becomes difficult to secure the reliability of connection between the conductor layers and the terminal electrodes.
According to the technique disclosed in JP 10-163002A or JP 11-003833A, it is possible to increase the areas of the regions in which the conductor layers touch the terminal electrodes, but the amount of increase in the areas is very small. It is therefore difficult to secure a satisfactory degree of reliability of connection between the conductor layers and the terminal electrodes through the use of the technique disclosed in JP 10-163002A or JP 11-003833A.
According to the technique disclosed in JP 2-121313A or JP 5-129149A, it is possible to increase the areas of the regions in which the conductor layers touch the terminal electrodes, compared with the case in which the terminal electrodes touch only the end face of one of the conductor layers. However, the technique disclosed in JP 2-121313A or JP 5-129149A is applicable only to cases in which there are a plurality of conductor layers forming one of electrodes of a single capacitor in the circuit. It is difficult to reduce the size and profile of the thin-film device when there are a plurality of conductor layers forming one of electrodes of a single capacitor in the circuit.